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Forum topic by Alster posted 07-23-2011 09:09 PM 1186 views 1 time favorited 12 replies Add to Favorites Watch
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Alster

99 posts in 2677 days


07-23-2011 09:09 PM

One of my big areas of inexperience is glueing up panels. I’ve done it, but I’m not very good at it. I’ve read very mixed things, in particular, about clamp pressure. Fine Woodworking did a test that concluded that the best bond comes from using just about as much clamp pressure as you can generate. But in the old days, a simple rub joint was often used.

Here’s my real problem: when I clamp down reasonably hard using my pipe clamps, I always seem to introduce a bit of bow into the panel, even when using cauls at the ends of the boards. Of course, this is a bigger problem with things like tabletops than with small panels made of just a couple of boards.

Seems like everybody glues up panels with little problem. Am I the only doofus too dumb to do this right? And if so, what can I do to fix it?


12 replies so far

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mtenterprises

933 posts in 2155 days


#1 posted 07-23-2011 09:25 PM

Here is an idea I have used extensivly that I found in “Fine Woodworking on Proven Shop Tips” and as my note on the pic says it does work great. You can make these as big or small as you need and they actually apply a great amount of pressure. The only differance I did was to use double wedges instesd of single, one wedge on top of and reversed from the other. The other thing that you want to do is put culs on the sides where the rope can dig into your material.
Good Luck

MIKE

-- See pictures on Flickr - http://www.flickr.com/photos/44216106@N07/ And visit my Facebook page - facebook.com/MTEnterprises

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Grandpa

3256 posts in 2138 days


#2 posted 07-23-2011 09:31 PM

The better the clamp the better the glue up. The clamps we buy at Harbor Freight are not the same as Pony clamps. They look the same but they have looser tolerances and cause deflection. this gives the bowing action. the I-Beam clamps have little deflection. Pipe clamps more. the longer the clamping surface the more it can deflect because it has a longer lever. By lever I mean the distance from the beam or bar going outward. It works like any lever would. keep all the wood low in the clamp jaws and use clamps on both sides of the wood. use cauls and not too much pressure or you get deflection.

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Loren

8302 posts in 3110 days


#3 posted 07-23-2011 09:59 PM

In the old days they used hide glue. It grabs and sets pretty fast so you don’t
have time to fool around with clamps.

I’ve done rubbed joints. They are good but your craftsmanship has to
be spot-on. I’ll argue that rubbed joints should be cut with a hand plane
only because a jointer leaves ripples.

These modern glues are much easier to work with casually than hide glue,
but they do require more time in the clamps.

I have a Plano clamp and it makes clamping panels so much faster and less
aggravating it’s not even funny. Pipe clamps are pretty much bottom of
the barrel. You can get by with them, but when you get some real
good clamps you’ll avoid the pipe clamps like the plague ‘cept when you’‘ve
run out of the good clamps.

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jusfine

2405 posts in 2388 days


#4 posted 07-23-2011 10:07 PM

Loren, I haven’t seen anyone reference a Plano clamp in years, I also have one in my shop and agree they are the best for panels, so quick and simple…

-- Randy "You are judged as much by the questions you ask as the answers you give..."

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Grandpa

3256 posts in 2138 days


#5 posted 07-23-2011 10:18 PM

I agree Loren, so why is it people here pay thousands for table saws or jointers and then go to Harbor Freight to get the cheapest clamps on the market?

View Lee Barker's profile

Lee Barker

2170 posts in 2313 days


#6 posted 07-23-2011 11:12 PM

Are your boards coming off a jointer, and are they dead solid square? If they’re not, that’s where the bow originates, then it’s amplified by clamp pressure.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View PurpLev's profile

PurpLev

8523 posts in 3111 days


#7 posted 07-23-2011 11:15 PM

if you get a bow it means your clamps are not aligned with the center of your boards. like bentlyj said – bump up the boards with some spacers so that the clamps jaw center is centered with the thickness of the boards. then alternate the placement of the clamps – some below the boards, some above (so any bowing action would be sort of cancelled out so to speak)

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View ChuckM's profile

ChuckM

577 posts in 3129 days


#8 posted 07-24-2011 02:28 AM

The LV newsletter carries an article on clamping and clamping jigs such as alignment blocks in its latest issue. Check that out and it may help:

http://www.leevalley.com/en/newsletters/Woodworking/5/6/article3.htm

Here’s a trick you can use to ensure the clamping force is centered at the stock: if your stock is 3/4”, place a 3/4” dowel between the clamp head and the board before you tighten the clamp. Likewise, use a 1/2” dowel if your board is 1/2” thick.

I also find parallel clamps better for the job of edge gluing than pipe clamps. You can never have enough // clamps!

P.S. Did you do a dry run before you opened your glue bottle? Not doing so is the #1 mistake on a glue-up job. A dry run would enable you to find out potential problems due to your clamps or joints or what not, allowing you to fix them before it’s too late.

-- The time I enjoy wasting is not time wasted

View shipwright's profile

shipwright

7168 posts in 2260 days


#9 posted 07-24-2011 02:31 AM

Do the learning curve with hide glue. You won’t regret it. It does so many things so well.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

View ScottN's profile

ScottN

261 posts in 2142 days


#10 posted 07-24-2011 02:52 PM

I use pipe clamps. I place the pipe clamps about 12” apart on the bottom of my glue ups and the same on the top.

-- New Auburn,WI

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DLCW

530 posts in 2117 days


#11 posted 07-25-2011 01:25 AM

I use Bessey clamps and pipe clamps for large panels. I make sure the edges are perfectly straight and 90 degrees to the face of the board. Even a tenth of a degree off can make the clamp up bow. I then apply a bead of glue (I don’t spread it out like many people do). I get it as close to center as I can.

Then I apply my clamps and apply just enough pressure to get a tiny bead of squeeze out on both sides. This way I know every bit of surface area inside the joint as glue coverage and I’m not ratcheting down so hard that I’m squeezing all the glue out and starving the joint. To much clamping pressure will do this.

I don’t understand the philosophy of squeezing so hard that all the glue comes out – never has made sense to me.

-- Don, Diamond Lake Custom Woodworks - http://www.dlwoodworks.com - "If you make something idiot proof, all they do is make a better idiot"

View GregD's profile

GregD

783 posts in 2599 days


#12 posted 07-25-2011 02:54 AM

My first experience gluing panels was a few months ago. I did a batch of 18 panels for a large door. The panels were 24” along the grain and 10” wide.

For the stock prep I flattened and thicknessed the boards. When I jointed the edges I ran the top of one board against the fence and the bottom of the mating board against the fence. Ideally that should cancel out any error in my fence setup, although I think I have it pretty square.

For clamping I used a pair of these . When I made my cauls I ripped 2×4s and jointed the sides that would be up against the panels. I also used 8 strips of wood about 3/4” wide and about 3/8” thick – but I ran them through my thickness planer to make sure they were of uniform thickness. I used the 8 strips as spacers that run the length of the panels, parallel to the glue joint an near the edges of the boards. These spacers keep any cauls that cross the glue line from contacting any squeeze out.

I would start the clamp up by camping blocks across the glue joint at each end of the assembly in order to keep the boards aligned. The blocks clamped against the 4 spacer strips on either side of the joints, 2 on top, 2 on bottom, These boards were narrow enough so that my large Kreg clamp could reach the center of the joint, so I also clamped blocks across the joint there. I then applied the 4 way clamps and made them both equally tight. For good measure I added more bar clamps to increase the pressure on the joint. I alternated the bar clamps – one over the top, the next under the bottom.

I applied quite a bit of pressure and did not notice any significant bowing when I went to flatten the glued-up panels.

-- Greg D.

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